Serum immunoglobulin levels in nude mice

Fatal autoimmunity in mice reconstituted with human hematopoietic stem cells encoding defective FOXP3

Mice reconstituted with a human immune system provide a tractable in vivo model to assess human immune cell function. To date, reconstitution of murine strains with human hematopoietic stem cells (HSCs) from patients with monogenic immune disorders have not been reported. One obstacle precluding the development of immune-disease specific "humanized" mice is that optimal adaptive immune responses in current strains have required implantation of autologous human thymic tissue. To address this issue, we developed a mouse strain that lacks murine major histocompatibility complex class II (MHC II) and instead expresses human leukocyte antigen DR1 (HLA-DR1). These mice displayed improved adaptive immune responses when reconstituted with human HSCs including enhanced T-cell reconstitution, delayed-type hypersensitivity responses, and class-switch recombination. Following immune reconstitution of this novel strain with HSCs from a patient with immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, associated with aberrant FOXP3 function, mice developed a lethal inflammatory disorder with multiorgan involvement and autoantibody production mimicking the pathology seen in affected humans. This humanized mouse model permits in vivo evaluation of immune responses associated with genetically altered HSCs, including primary immunodeficiencies, and should facilitate the study of human immune pathobiology and the development of targeted therapeutics.

T cells are required for the peripheral phase of B-cell maturation

B-lymphocyte maturation is considered to be independent of the thymus. However, there is circumstantial evidence suggesting that it may be impaired in nude animals that lack the thymus. Our study shows that the proportion of immature B-lymphocyte subsets (CD90(high) IgM(high) and CD90(high) IgM(low)) was significantly increased, whereas that of mature B-lymphocyte subsets (CD90- IgM(low) and CD90- IgM(high)) was decreased in the blood and lymph nodes of nude rats. In addition, the expression of major histocompatibility complex class II, intercellular adhesion molecule-1, CD44 and l-selectin was significantly down-regulated both on immature and mature B-lymphocyte subsets. After implantation of thymic tissue under the kidney capsule of nude rats the block in B-lymphocyte maturation was alleviated and the expression of surface molecules was normalized. Comparable effects were seen after the adoptive transfer of T lymphocytes. Thus, we show that in nude rats B cells do not mature properly because of the lack of T-cell help and that T lymphocytes are required for the peripheral phase of B-lymphocyte maturation, as well as for the appropriate expression of surface molecules. This should be considered when treating patients with T-cell deficiencies.

Comparison of the indigenous oral microbiota and immunoglobulin responses of athymic (nu/nu) and euthymic (nu/+) mice

The role of the immune system in the homeostasis of indigenous oral bacterial populations is poorly understood. In this study, we compared the evolution of the indigenous oral microbiota of specific pathogen-free athymic nude (nu/nu) BALB/c mice with that of their corresponding phenotypically normal (nu/-) littermates. We also evaluated corresponding salivary and serum antibody activities (IgA and IgG) against the predominant indigenous oral bacteria. The bacterial species recovered from the two mouse strains were Lactobacillus murinus, Enterococcus faecalis, Streptococcus oralis and Staphylococcus epidermidis. From 27 days of age, nu/+ and nu/nu mice had significantly different proportions of oral bacterial populations. When the microbiota stabilized (at 40 days of age), the total cultivable microbiota of nu/+ mice was dominated by L. murinus (65-85%), while that of nu/nu mice was dominated by E. faecalis (40-60%). The precise factors that alter the oral resident microbiota in nu/nu mice are unknown. We found that total salivary IgA levels were significantly lower in nu/nu mice, but no association were observed between the level of salivary IgA antibody against indigenous bacteria and the proportion of these indigenous bacteria in the oral microbiota. The change in the microbiota of nude mice may have been caused by other factors such as defects in other immune functions or cold stress.

Germinal center formation, immunoglobulin class switching, and autoantibody production driven by "non alpha/beta" T cells

The production of class-switched antibodies, particularly immunoglobulin (Ig) G1 and IgE, occurs efficiently in T cell receptor (TCR) alpha-/- mice that are congenitally devoid of alpha/beta T cells. This finding runs counter to a wealth of data indicating that IgG1 and IgE synthesis are largely dependent on the collaboration between B and alpha/beta T cells. Furthermore, many of the antibodies synthesized in TCR alpha-/- mice are reactive to a similar spectrum of self-antigens as that targeted by autoantibodies characterizing human systemic lupus erythematosus (SLE). SLE, too, is most commonly regarded as an alpha/beta T cell-mediated condition. To distinguish whether the development of autoantibodies in TCR alpha-/- mice is due to an intrinsic de-regulation of B cells, or to a heretofore poorly characterized collaboration between B and "non-alpha/beta T" cells, the phenotype has been reconstituted by transfer of various populations of B and non-alpha/beta T cells including cloned gamma/delta T cells derived from TCR alpha-/- mice, to severe combined immunodeficient (SCID) mice. The results establish that the reproducible production of IgG1 (including autoantibodies) is a product of non-alpha/beta T cell help that can be provided by gamma/delta T cells. This type of B-T collaboration sustains the production of germinal centers, lymphoid follicles that ordinarily are anatomical signatures of alpha/beta T-B cell collaboration. Thus, non-alpha/beta T cell help may drive Ig synthesis and autoreactivity under various circumstances, especially in cases of alpha/beta T cell immunodeficiency.

Experimental Yersinia enterocolitica infection in euthymic and T-cell-deficient athymic nude C57BL/6 mice: comparison of time course, histomorphology, and immune response

To elucidate the role of T lymphocytes in primary infection with Yersinia enterocolitica, we investigated the elimination rate of this pathogen, the histomorphology of tissue lesions, and the immune responses of athymic T-cell-deficient C57BL/6 nude mice and their euthymic littermates after parenteral infection with Y. enterocolitica of serotype O:8. While a low inoculum of 3 x 10(2) Y. enterocolitica cells (about 0.01 times the median lethal dose for normal C57BL/6 mice) was cleared by normal C57BL/6 mice within 7 to 10 days, athymic nude C57BL/6 mice developed progressive infections after this inoculum, leading to death on days 20 to 25 postinfection (p.i.). While normal C57BL/6 mice experienced short-term transient infections, nude mice exhibited a biphasic, progressive infectious process. Thus, in the early phase (days 1 to 7 p.i.), a rapid influx of CD11b/18-positive cells (Mac-1 antigen) and natural killer cells was evident in the spleens and livers of the nude mice. The late phase (from day 8 p.i. onward) was characterized by a rapid progression of the infection and a further influx of CD11b/18-positive cells into the liver accompanied by an increase in bacterial counts and development of tissue lesions particularly in the liver and spleen. In normal mice, granuloma-like lesions composed of CD11b/18-, CD4-, and CD8-positive cells could be observed. However, granulomata were not found in nude mice. Yersinia-specific immunoglobulin G antibodies appeared on day 15 p.i. in the sera of normal mice, while nude mice failed to develop significant antibody titers. Adoptive transfer of Yersinia-specific T cells into athymic nude mice mediated resistance to Y. enterocolitica infection and restored both the ability of granuloma formation and the production of specific antibodies. In summary, the data presented herein strongly suggest that T lymphocytes play an essential role in the defense of C57BL/6 mice against Y. enterocolitica.

Organization and growth of mammary epithelia in the mammary gland fat pad

Mammary gland development consists of a series of very highly ordered events involving interactions among a number of distinct cell types. An important aspect of mammary gland development is that the mammary gland consists of a fat pad of mesodermal origin into which epithelial cells of ectodermal origin proliferate. This proliferation of epithelial cells into the mammary fat pad is the subject of this review. The nature of the stroma into which epithelial cells proliferate is of considerable importance in determining the structure of the resulting gland. In mice, white adipose tissue appears to be required for normal mammary development. Transplantation of mammary epithelia to other types of stroma does not support epithelial growth or result in abnormal growth. To date, a synthetic substratum capable of mimicking white adipose tissue has not been developed. Although collagen gel cultures are generally considered superior to glass or plastic substratum in supporting near normal epithelial growth, the technique has not advanced to the point that the in vivo growth pattern is duplicated. Recent research on the generation of chimeric mammary tissue (by transplanting mammary epithelia from rats, cows, and women to the mammary fat pads of athymic nude mice) suggests that there are important species differences in the stromal requirements for mammary gland development. In particular, extensive and expansive growth of rat mammary tissue is observed in mouse mammary fat pads. However, the mouse mammary fat pad appears incapable of supporting expansive growth of bovine or human mammary epithelia. The reason for this difference is not clear. However, human and bovine mammary epithelia may require the presence of more fibrous (collagenous) tissue than rodent mammary epithelia for normal proliferation.

T-cell-dependent modulation of the polyclonal B-lymphocyte responses in normal spleen cell cultures stimulated by lipopolysaccharide

The in vitro polyclonal B-cell proliferative and plaque-forming cell (PFC) responses to the T-independent (TI) mitogen lipopolysaccharide (LPS) are increased by the addition of normal syngeneic splenic T cells. Normal irradiated Lyt-2- T cells also alter the IgG subclass distribution from the typical predominance of IgG3 and IgG2b PFC to the appearance of IgG1, IgG2a and IgA PFC in T-cell-depleted spleen cell (SC) cultures. Furthermore, secondary LPS blast cultures yield increased PFC responses when co-cultured which syngeneic fresh normal T cells which, even in the absence of mitogen, induce PFC responses in such activated B cells. As LPS blasts induce normal syngeneic T cells to proliferate and significant numbers of L3T4+ blast cells are found in LPS-stimulated normal spleen cell cultures, we conclude that T cells actively participate in the regulation of these responses. The significance of these findings for the regulation of TI responses in vivo by "autoreactive" T cells is considered.

Ontogenic development of "natural" and induced plaque-forming cell isotypes in normal mice

The numbers of cells and background plaque-forming cells (PFC) in the spleen of C3H/HeJ mice increase exponentially during the first 2 weeks after birth, but much slower in bone marrow (BM). IgG1 and IgG2a PFC are the first non-IgM PFC detectable, while IgG3 and IgA PFC appear only around weaning. Adult-type PFC numbers and isotype pattern are present in spleen and BM at 4 and 15 weeks, respectively. Neonatal splenic C3H/Tif B cells produce non-IgM Ig classes in vitro in response to polyclonal activation by lipopolysaccharide or by helper T cells. These responses are of low magnitude during the first 2 weeks of life, but both secreted and membranebound IgG1 and IgG3 isotypes are detectable already a few days after birth, in a pattern that is identical to that typical of T cell-dependent or independent responses of adult cells. These results indicate full maturity of B cells in "switch" abilities already from birth, in spite of a general deficiency in terminal maturation. In addition, they demonstrate the complexity of isotype regulation in "background" antibody production in vivo.

Mucosal immunoregulation: environmental lipopolysaccharide and GALT T lymphocytes regulate the IgA response

In this review, we have emphasized: 1) bacterial lipopolysaccharide (LPS) involvement in IgA responses to orally administered thymic-dependent (TD) antigens; 2) characterization of Peyer's patch (PP) lymphoreticular cells; and 3) gastrointestinal immunization with gram negative pathogens and anti-LPS immunity to infection. Gut LPS, which interacts with PP lymphoreticular cells, is a major determinant for host responses to orally administered TD antigens. Bacteroides species are the principal microflora present in the gastrointestinal tract and our studies with phenol-water LPS extracts from Bacteroides fragilis indicate that both polysaccharide and lipid A activate lymphoreticular cells. The B. fragilis lipid A moiety, like that derived from E. coli and Salmonella LPS, induces B cell mitogenic responses in cultures from LPS responsive mice, but does not stimulate C3H/ H3J B cells. The inability of lipid A to stimulate gut-associated lymphoreticular tissue (GALT) cells of C3H/HeJ mice results in the induction of greater T helper cell activity in this tissue in response to orally administered TD antigens and ultimately results in an elevated IgA response pattern. Murine PP contain accessory cells (approximately 1% dendritic cells and 6-8% macrophages) and lymphocytes T (35-38%) and B (40-42%). Recent studies with antigen-specific T cell clones from C3H/ H3J PP have resulted in the isolation of IgA isotype-specific T helper cells (PP Th A cells). PP Th A cells are antigen-specific, bear Fc alpha receptors, and require H-2 histocompatibility with B cells for helper activity. PP Th A cells most effectively collaborate with surface IgA (sIgA)-bearing B cells (IgA committed B cells) for IgA isotype responses. Other studies have shown that PP dendritic cells and T cells form clusters when stimulated in vitro with sodium periodate and that these clusters promote polyclonal IgA responses in B cell cultures. Polyclonal IgA responses in cultures containing PP cell clusters from C3H/ H3J mice are considerably higher than those in identical cultures from LPS responsive mice. In other studies, the environmental influence on GALT B cells and their resultant commitment to IgA isotype is under investigation. CBA/N, X-linked immunodeficient (xid) mice possess an immature splenic B cell population which cannot respond to thymic-independent class-2 (TI-2) or certain TD antigens. However, GALT B cells of xid mice possess a mature Lyb-5+ B cell subpopulation capable of both TI-2 and TD responses.(ABSTRACT TRUNCATED AT 400 WORDS)

Immune response to bacterial dextrans. II. T cell control of antibody isotypes

The isotype distribution of Dextran B 512 (Dex)-specific plaque-forming cells (PFC) and serum antibodies was studied after in vivo immunization in C57BL/6 mice. Although IgG2b and IgG3 could also be detected in most individuals, the majority of non-IgM PFC were of the IgA isotype. All classes other than IgM were T cell-dependent, as shown by their complete absence in athymic "nude" mice. This unusual isotype pattern was further investigated by studying the antibody responses to the same Dex epitope coupled to a protein carrier, and to a different hapten coupled to the carrier Dex or to a protein. The results show that IgA responses are epitope-related and selectively associated with anti-Dex antibodies: no IgA PFC are detected against a hapten coupled to Dex or proteins, while the enhanced levels of helper cell reactivity provided by protein carrier to Dex result in the appearance of IgG1 antibodies in addition to IgA. These results indicate that T cells that modulate isotype patterns in these responses can discriminate between Dex- and DNP-specific B cells in the response to the same carrier. Since the same idiotype is detected on a large fraction of the IgM and IgA anti-Dex response and antiidiotypic helper cells have previously been detected in normal C57BL/6 mice, we suggest that idiotype-specific T cells control the production of IgA antibodies upon immunization with Dex.

Mouse IgG antibodies have subclass associated affinity differences

Subclasses of IgG were separated from pools of mouse sera by letting immunoglobulins absorb on protein A-Sepharose and by eluting with buffers of decreasing pH. Most donor mice were immunized with a conjugate of a hapten (NIP) and chicken gamma globulin 20 days previously. The results indicate that concentrations of IgG varied from 5.1 to 8.6 mg/ml in the pools of immune sera and was 3.0 mg/ml in one normal serum tested. One half of this was IgG1, ca. 20% of IgG2a and IgG2b each, and 10% IgG3 in the pools of BALB/c sera. IgG2a and IgG3 could not be separated from C57BL sera (due to allotype b), but their combined share of IgG appears to be higher than in BALB/c. Immune sera contained 0.5-1.6 mg/ml of anti-NIP antibodies. Of this 90-98% was IgG1 and the remainder was split between the other subclasses. Up to one half of the protein in the IgG1 fraction was anti-NIP antibody. This surprising finding was confirmed by demonstrating that nearly 50% of the u.v.-light absorption was specifically removed by a NIP-immunosorbent. Subclass-associated affinity-differences were observed. IgG1 anti-NIP had a greater average affinity than IgG2a anti-NIP antibodies. The difference was ca. 1.5-fold when the equilibrium dialysis was focusing on the high-affinity bracket of the total population (concentration of free hapten 16-200 nM). At higher hapten concentrations the trend was the same but the data are fewer. Antibodies in subclasses IgG2b and IgG3 appear to share the lower affinity of IgG2a.

Cimetidine and the immune response. I. In vivo augmentation of nonspecific and specific immune response

Cimetidine is a commonly prescribed histamine antagonist useful in the treatment of peptic ulcer disease. Histamine receptors are found on suppressor T cells and therefore we expected to observe enhanced immune responsiveness in animals treated with this drug. Mice given daily subcutaneous injections of cimetidine (25 or 100 mg/kg) were found to produce approximately twice as much specific antibody in response to tetanus toxoid immunization. Furthermore, mitogen-stimulated splenocytes from cimetidine-treated animals proliferated to a greater extent and produced more immunoglobulin in vitro than controls. These observations offer direct in vivo evidence for immunomodulation by cimetidine.

The immunogenicity of carcinoembryonic antigen (CEA) in athymic nude mice

Experiments were carried out to determine whether athymic nude (nu/nu) mice are capable of producing circulating antibodies to carcinoembryonic antigen (CEA). By a double antibody radioimmunoassay technique, no antiCEA activity was detected in the sera of normal nude mice, nude mice bearing any one of four types of CEA positive human colonic tumour xenografts or nude mice immunized with a purified CEA preparation. Conversely, we were able to demonstrate antiCEA activity in the sera of euthymic (+/+) Balb/c and heterozygote nude (nu/+) mice immunized by the same schedule. We conclude that nude mice do not produce significant amounts of circulating antiCEA in response to CEA, whether present in colorectal tumour xenografts or in the immunization schedule used. The immunogenicity of CEA in other xenograft systems and man is compared and contrasted to that in the nude mouse, and the significance of differences discussed with respect to the use of the nude-mouse-human-xenograft system as a model for human colonic cancer.

Effect of neonatal thymectomy on immune responses of rats to Streptococcus mutans

The effect of neonatal thymectomy on secretory and systemic antibody responses in rats was studied. Groups of normal or thymectomized (Tx) rats were infected or immunized and infected with Streptococcus mutans 6715. Tx rats exhibited a significantly lower level of salivary immunoglobulin A (IgA) antibody to S. mutans after a 45- to 65-day infection. Similarly, after multiple local injections of formalinized S. mutans, Tx rats showed a delay in the appearance and lower levels of salivary IgA antibody to S. mutans. Serum IgG antibody levels were also decreased in Tx rats with both experimental protocols. In contrast, salivary IgG and serum IgM anti-S. mutans activity in Tx and normal rats were similar during the experiments. These results demonstrated that thymus deprivation at birth produces profound effects on the ability of rats to manifest secretory IgA antibody responses to the pathogenic microorganism S. mutans.

Change in the humoral response of athymic nude mice with ageing

The evolution of the serum Ig levels of Balb/c-nu/nu mice was investigated between 1 month and 12 months of age. An increase as a function of age was observed in all classes and subclasses, which was, expressed in percentage of a nu/+ serum, from 130% to 230% for IgM, from 3% to 24% for IgG1, from 12% to 164% for IgG2a, from 28% to 62% for IgG2b, and from 10% to 50% for IgA. This increase correlates with an increase of plasma cells of each class in the bone marrow, whereas the number of plasma cells in the plasma cells in the spleen, the lymph node, and the intestinal mucosa did not change markedly with age. The humoral response after an injection of heterologous erythrocytes was compared in young and aged nu/nu mice; aged mice had a higher haemagglutination titre mainly due to direct (IgM) antibodies. The response of the spleen, as judged by plaque-forming cells (PFC), was similar in young and aged mice, but the bone marrow response, not detectable in young mice, was about as high in aged nude mice as in nu/+ mice. Although the content of Thy 1 cells in the spleen and lymph nodes was markedly higher in aged than in young nude mice, no T-cell function could be detected at any age, either in the response to phytohaemagglutinin or concanavalin A or in a graft-versus-host assay. Increase in the Ig production with age is interpreted as the result of progressive priming and hyperimmunization by environmental antigens, leading to a T-independent immune response (even against antigens considered to be T-dependent) predominantly located in the bone marrow.

Prevention of immunoglobulin production by allotype-dependent T cells

Adoptive lymphocyte transfers between Iga, Igb and Igd allotype-congenic mouse strains revealed host barriers against the production of certain donor allotypes. First, as recipients of Igb cells, Iga and Igd mice permitted the production of donor Ig-4b but not that of Ig-1 b. The apparent mediators of this Ig-1 b barrier were T cells specific for Ig- 1 b determinants on B cells. Additional cell transfers showed Iga mice to have a second barrier against allotype production by Igd donor cells. Reciprocal cell transfers showed Igb and Igd mice to have comparatively weak barriers against Iga-producing cells. As host barriers were absent in mice deficient for T cells (athymic nude mice), it appears that they are T cell-mediated. Further, the allotype-dependence of such barriers means that the antigens responsible must be under the control of allotype-linked genes. The regulatory implications of this for the immune system are discussed.

The immunosuppressive role of alpha-fetoprotein during pregnancy

Cell-mediated and humoral immune responses were assessed in mice at mid-term (day 10) in pregnancy. A significant but selective suppression of the primary in vivo antibody (plaque-forming cell) response to SRBC was observed, with the most pronounced effect being on the gammaA response. Similar results were obtained for secondary in vitro antibody synthesis by antigen-primed spleen cells from pregnant mice, demonstrating the intrinsic nature of the inhibition. Pregnant mouse serum (PMS) was shown to suppress primary in vitro antibody synthesis, and the inhibitory effect was abrogated by the selective removal of alpha-fetoprotein (AFP) using affinity chromatography. Normal mouse serum became similarly suppressive in vitro when purified AFP of fetal origin was added to it in concentrations approximating that found in PMS. Spleen cells from pregnant mice showed a suppressed mitogenic response to phytohemagglutinin, a lowered response to concanavalin. A, and a normal response to lipopolysaccharide. In contrast, the allogeneic response of these animals as measured in the one-way mixed lymphocyte culture was enhanced. PMS suppressed both allogeneic and mitogen-induced lymphocyte transformation by spleen cells from nonpregnant mice, and the effect was eliminated by the selective removal of AFP. These findings indicate an important functional role for AFP in normal embryological development.